I do realize each seller is different, but I was wondering if there was a general consensus on what was the best and worst part about buying online. What specific questions did you ask? And arrangements prior a purchase, did you get these agreements in writing or verbal agreement? Just wondering

I use GunsAmerica all the time.  You have a 3 day period for inspection but I have never had a problem with buying or selling.  Make sure you use a postal money order in case of fraud.

You might consider auctionarms.com too.

I had a really good experience on GunsAmerica, But I was the seller, basically the buyer emailed me and we exchanged information and he then called me we talked and made arrangements, everything went really smooth. GunBroker is a Bidding site I believe which maybe a bit different, but like you said it all depends on the Buyer or seller. I had a another good experience on Auctionarms.com too, its alot like EBAY.

I have used GunsAmerica.com to purchase firearms numerous times. I do not use GunBroker.com for firearms, as I do not like bidding on them.

As for questions prior to purchase, my first question is always,"Do you still have such and such firearm for sale?" If the seller still possesses it, then I proceed to ask about the condition of it, approximate rounds put through it, and it's maintenance history. I also request photos of the actual rifle being sold. If I'm pleased with the answers I receive, then I try to work out a deal on the price. If the seller and I agree upon a price and on who pays the shipping, etc. then I request the seller's name, address, and telephone number and provide like data about myself for seller. I then get a copy of my dealer's FFL and a postal money order and send it to the seller "overnight". I let them know that payment has been sent and request that they keep in touch in regards to receiving the payment and FFL copy, and to let me know when it ships.